Calculating force of the femur on the knee cap.

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The discussion focuses on calculating the force of the femur on the kneecap given specific angles and muscle force. The user initially calculated the x and y components of the force but arrived at an incorrect answer. They used the equations of motion and the forces acting on the system, including the angles of the tendon. A suggestion was made to reduce the number of significant digits in their calculations, indicating that precision may have affected the results. The conversation emphasizes the importance of correctly applying physics principles to solve for forces in a biomechanical context.
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Homework Statement


The diagram of the leg shows the femur (1) and tibia (2). The quadriceps muscle (3) applies a force to the lower leg via a tendon (4) that is embedded with the kneecap (5). If the force applied by the muscle to the tendon is FM = 420 N, what is the force of the femur on the kneecap? A simplified model of the leg is shown next to the diagram. The leg bones are represented by two beams attached by a pin. The tendon is modeled by a rope and the kneecap acts like a pulley. The tendon above the kneecap makes an angle θ1 = 23° with respect to the vertical, and the portion of the tendon below the kneecap makes an angle of θ2 = 24° with respect to the vertical. Enter the x component, followed by the y component.

knee.gif



Homework Equations



fnet=ma



The Attempt at a Solution



I tried:

Fx= max
T1x + T2x + Ffemurx=0
-240sin23 -240sin24 + Ffemur= 0
-93.78 - 97.62 + Ffemur=0
Ffemur= 191.4N

Fy=may
T1y + T2y + Ffemury=0
240cos23 - 240cos24 + Ffemury=0
220.92 - 219.25 + Ffemury=0
Ffemury= -1.67N

I didn't get the right answer..

please help!
 
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Supposed that the tension is the same all along the tendon, and x means horizontal , y means vertical component of force, your solution looks correct. Try to use less significant digits.

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